Don't drop debug_info when posting to sync server fails

sync/test/engine/mock_connection_manager.cc

Index: sync/test/engine/mock_connection_manager.cc
diff --git a/sync/test/engine/mock_connection_manager.cc b/sync/test/engine/mock_connection_manager.cc
index 624e02218822a9c2fc9509f10280222fbabb5915..434f6c36fc692b5047fe11442a8a50276bdf657e 100644
--- a/sync/test/engine/mock_connection_manager.cc
+++ b/sync/test/engine/mock_connection_manager.cc
@@ -83,7 +83,8 @@ bool MockConnectionManager::PostBufferToPath(PostBufferParams* params,
   CHECK(post.has_protocol_version());
   CHECK(post.has_api_key());
   CHECK(post.has_bag_of_chips());
-  last_request_.CopyFrom(post);
+
+  requests_.push_back(post);
   client_stuck_ = post.sync_problem_detected();
   sync_pb::ClientToServerResponse response;
   response.Clear();
@@ -686,6 +687,17 @@ const CommitResponse& MockConnectionManager::last_commit_response() const {
   return *commit_responses_.back();
 }
 
+const sync_pb::ClientToServerMessage&
+    MockConnectionManager::last_request() const {
+  EXPECT_TRUE(!requests_.empty());
+  return requests_.back();
+}
+
+const std::vector<sync_pb::ClientToServerMessage>&
+    MockConnectionManager::requests() const {
+  return requests_;
+}
+
 bool MockConnectionManager::IsModelTypePresentInSpecifics(
     const google::protobuf::RepeatedPtrField<
         sync_pb::DataTypeProgressMarker>& filter,